An ornithopter is a type of
flying machine that attempts to fly by imitating the flapping of a bird's
wings. It was first devised by Leonardo da Vinci in the late 1400s, and many
others tried unsuccessfully during the 1800s to fly this type of aircraft.

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An ornithopter -- it's every bit as impractical as it
looks.

Some ornithopters were
propelled with oars; others used the arms and legs of the occupants for power.
Some ornithopters were to be used with the aid of an inflated balloon. The
word comes from the Greek words for bird and wing.

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This sketch by Leonardo da Vinci shows his design for a
14.th century ornithopter flying machine

Edward Frost of Cambridgeshire,
England, constructed an ornithopter of willow, silk, and feathers in 1902.
Frost was later president of the Royal Aeronautical Society.

Credits
- Gary Bradshaw; To Fly Is Everything

The Ornithopter

An ornithopter (from Greek ornithos "bird"
and pteron "wing") is an aircraft
that flies
by flapping its wings. Designers seek to imitate the flapping-wing flight of
birds, bats, and insects. Though machines may differ in form, they are usually built on
the same scale as these flying creatures. Manned ornithopters have also been
built, and some successful flights have been reported.

The Early History Of The Ornithopter

The idea of constructing wings in order to imitate the
flight of birds dates to the ancient Greek legend of Daedalus
and
Icarus. The first attempt at mechanical flight is attributed to
Abbas Ibn Firnas, who launched a rudimentary ornithopter from the Mount
of the Bride (Jabal al-'Arus) in the Rusafa Area, near Córdoba, Spain in 875
AD.
Roger Bacon, writing in 1260, was among the first to consider a
technological means of flight. Around 1490,
Leonardo da Vinci began to study the flight of birds. He grasped that humans are
too heavy, and not
strong enough, to fly using wings simply attached to the arms. Therefore
he proposed a device in which the aviator lies down on a plank and works two
large, membranous wings using hand levers, foot pedals, and a system of
pulleys.

The first ornithopters capable of flight were constructed in France in
the 1870s.
Gustave Trouvé's 1870 model flew a distance of 70
meters in a demonstration for the French Academy of Sciences. The wings
were flapped by gunpowder
charges activating a
bourdon tube. Jobert in 1871 used a
rubber band to power a small model bird. Alphonse Penaud, Hureau de
Villeneuve, Victor Tatin, and others soon followed with their own designs.

Around 1890,
Lawrence Hargrave built several ornithopters powered by steam or
compressed air. He introduced the use of small flapping wings providing
the thrust for a larger fixed wing. This eliminated the need for gear
reduction, thereby simplifying the construction. To achieve a more birdlike
appearance, this approach is not generally favored today.

In the 1930s,
Erich von Holst carried the rubber band powered bird model to a high
state of development and great realism. Also in the 1930s,
Alexander Lippisch and other researchers in Germany
harnessed the piston internal combustion engine.

Manned Flight

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Schmid 1942 Ornithopter

The
UTIAS Ornithopter No.1

Perhaps because the prevailing technology is
fixed-wing aircraft, people are mainly aware of the failed attempts at
flapping-wing flight. This article describes only the more successful
attempts. The machines are of two general types: those with engines, and
those powered by the muscles of
the pilot.

In 1929, a man-powered ornithopter designed by
Alexander Lippisch flew a distance of 250 to 300 meters after tow
launch. The flight duration was necessarily short due to the limitations of
human muscle power. Since a tow launch was used, some have questioned
whether the aircraft was capable of sustained flight, however brief.
Lippisch asserted that the aircraft was actually flying, not making an
extended glide. Later tow-launched flights include Bedford Maule (1942),
Emil Hartmann (1959), and Vladimir Toporov (1993). All faced similar
limitations due to the reliance on human muscle power.

In 1942,
Adalbert Schmid flew a motorized, manned ornithopter at Munich-Laim. It
was driven by small flapping wings mounted at the sides of the fuselage,
behind a larger fixed wing. Fitted with a 3
hp Sachs motorcycle engine, it made flights up to 15 minutes
in duration. Schmid later constructed a 10 hp ornithopter based on the
Grunau-Baby IIa sailplane, which was flown in 1947. The second aircraft had
flapping outer wing panels.[1]

In 2005,
Yves Rousseau was given the Paul Tissandier Diploma, awarded by
the FAI for contributions to the field of aviation. Rousseau attempted his
first human-muscle-powered flight with flapping wings in 1995. On 20 April
2006, at his 212th attempt, he succeeded in flying a distance of 64 metres,
observed by officials of the Aero Club de France. Unfortunately, on his
213th flight attempt, a gust of wind led to a wing breaking up, causing the
pilot to be gravely injured and rendered
paraplegic.[2]

A team at the
University of Toronto Institute for Aerospace Studies, headed by Professor
James DeLaurier, worked for several years on an
engine-powered, piloted ornithopter. In July 2006, at the Bombardier
Airfield at
Downsview Park in Toronto,
Professor DeLaurier's machine, the
UTIAS Ornithopter No.1 made a jet-assisted takeoff and 14-second
flight. According to DeLaurier,[3]
the jet was necessary for sustained flight, but the flapping wings did most
of the work.[4]

Recent Developments

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George R. White and Canadian inventor Doug Froebe kept building these
feathered things well into the 1930s:

Practical applications capitalize on the resemblance to birds or insects.
The
Colorado Division of Wildlife has used these machines to help save the
endangered Gunnison Sage
Grouse. An artificial hawk under the
control of an operator causes the grouse to remain on the ground so they can
be captured for study.

Because ornithopters resemble birds or insects, they could be used for military
applications, such as spying
without alerting the enemies that they are under surveillance. AeroVironment,
Inc., led by
Paul B. MacCready (Gossamer
Albatross), has developed a remotely piloted ornithopter the size of a
large insect for possible spy missions.

MacCready also developed in the mid-1980s, for the
Smithsonian Institution, a half-scale
radio controlled replica of the giant pterosaur,
Quetzalcoatlus northropi. It was built to star in the IMAX movie
On the Wing. The model had a wingspan
of 5.5 meters (18
feet) and featured a complex,
computerized autopilot control system, just as the full-size pterosaur
relied on its neuromuscular system to make constant adjustments in flight.

Researchers hope to eliminate the motors and gears of
current designs by more closely imitating animal
flight muscles. Georgia Tech scientist
Robert C. Michelson is developing a
Reciprocating Chemical Muscle for use in micro-scale flapping-wing
aircraft. Michelson uses the term "entomopter"
for this type of ornithopter.
SRI International is developing polymer
artificial muscles which may also be used for flapping-wing flight.

In 2002, Krister Wolff and
Peter Nordin of
Chalmers University of Technology in Sweden,
built a flapping wing robot that learned flight techniques.[5]
The
balsa wood
design was driven by
machine learning
software technology known as a steady state linear
evolutionary algorithm. Inspired by natural evolution,
the software “evolves” in response to feedback on how well it performs a
given task. Although confined to a laboratory apparatus, their ornithopter
evolved behavior for maximum sustained lift force and horizontal movement.[6]

Since 2002, Prof. Theo Van Holten has been working on an ornithopter
which is constructed like a helicopter. The device is called the
ornicopter
[7] and was made by constructing the main
rotor so that it would have no reaction torque at all.

Aerodynamics

As demonstrated by birds, flapping wings offer potential advantages in
maneuverability and energy
savings compared with fixed-wing aircraft, as well as potentially vertical
take-off and landing. It has been suggested that these advantages are
greatest at small sizes and low flying speeds.

Unlike airplanes and helicopters, the driving airfoils
of the ornithopter have a flapping or oscillating motion, instead of rotary.
As with helicopters, the wings usually have a combined function of providing
both lift and thrust. Theoretically, the flapping wing can be set to zero
angle of attack on the upstroke, so it passes easily through the air.
Since typically the flapping airfoils produce both lift and thrust,
drag-inducing structures are minimized. These two advantages potentially
allow a high degree of efficiency.